HONG KONG (Reuters) - Missing China-born billionaire Xiao Jianhua was whisked in a wheelchair from a luxury Hong Kong hotel in the early hours of Jan 27 with his head covered, a source close to the businessman told Reuters.

Xiao was carried into his own car at the entrance to the Four Seasons serviced apartments in the heart of the Asian financial hub in what appeared to be a "smooth operation", another source with knowledge of the matter told Reuters.

The comments from the sources confirmed a report in the New York Times on the disappearance of Xiao, who has close ties to senior Chinese officials and their families.

Despite a statement issued in Xiao's name over 10 days ago that he was seeking medical treatment overseas and had not been abducted, his disappearance has rekindled fears over Hong Kong's status as an independent judicial entity of China.

"It is uncertain if Xiao was conscious when he left," the second source said, adding that it took at least a few people to carry the billionaire into the car.

"There was no struggle in the whole process. You could even say it was efficient. It was a smooth operation."

Reuters could not independently verify the circumstances at the time Xiao was taken out of the hotel or the condition of his health.

Assistants of Xiao were waiting in the lobby of the hotel's serviced apartments when at least five people, dressed in casual attire, came in, said the second source, who declined to be identified due to the sensitivity of the issue.

The group, which some media have reported were mainland Chinese agents, were escorted to Xiao's room by his assistants and they left shortly after with the businessman and some luggage, the second source said.

The source close to Xiao who said the billionaire left the hotel in a wheelchair said his head was covered with some cloth, but it was not clear what the material was. The source added that as far as he knew Xiao did not use a wheelchair and there was nothing wrong with his legs.

A Hong Kong police source who was briefed on the probe into Xiao's disappearance had previously told Reuters the case was initially treated as a "kidnapping" following a complaint from someone connected to Xiao.

But after a review of CCTV footage at the Four Seasons and at the border checkpoint, police concluded that Xiao had voluntarily left Hong Kong.

They said Xiao had entered mainland China through a border checkpoint on Jan 27 and that they were seeking more information on the case from Chinese authorities.

Police and the Four Seasons did not immediately respond to requests for comment on Saturday.

China's Ministry of State Security, Foreign Ministry and Public Security Bureau have so far not responded to Reuters requests for comment on whether Chinese agents were involved in Xiao's disappearance.

CORRUPTION CRACKDOWN

Xiao's disappearance has sparked widespread media speculation that he has been drawn into Chinese President Xi Jinping's crackdown on corruption, which has ensnared a string of Chinese executives.

Any indication that Xiao may have been forcibly removed from the former British colony would be a breach of the "one country, two systems" framework under which it has been governed since its return to mainland Chinese rule in 1997.

Xiao's case has already spooked many mainland Chinese working in the city, with some already making contingency plans and seeking advice on moving assets overseas.

Another source close to Xiao said his immediate family and the company's senior executives witnessed nothing unusual ahead of his disappearance.

Xiao's wife and brother were not in Hong Kong when he left the Four Seasons, the third source said, declining to say where they were at the time.

They immediately rushed back to Hong Kong, the source said.

"Everybody freaked out," the source said. "Nobody knew where he went, nobody knew what was happening."

Xiao's wife and brother have already "fled" Hong Kong to Canada, according to the third source.

Xiao's family, company executives and lawyers wrote a statement in Xiao's name "in a rush" to quell speculation that the billionaire had been kidnapped, the source said.

The statement, published on the front page of Hong Kong's Ming Pao newspaper five days after he went missing, said he was seeking medical treatment "outside the country" and "had not been abducted to the mainland."

It is uncertain if the family had been in touch with Xiao when the statement was drafted.

Outside law enforcement agencies, including those from mainland China, are not authorized to operate in Hong Kong, which enjoys wide-ranging freedoms not allowed on the mainland, including a separate legal system.

Police commissioner Lo Wai-chung said in a radio talk show last Saturday that there was no sign of mainland authorities enforcing the law in Hong Kong.

Xiao, who runs Tomorrow Holdings, a financial group headquartered in Beijing, was ranked 32nd on the 2016 Hurun China rich list, China's equivalent of the Forbes list, with an estimated net worth of $5.97 billion.

At least two of Tomorrow Group's statements posted after Xiao's disappearance on their social media account were deleted, pointing to what appears to be heightened sensitivity in Beijing over the case.